It appears the fancy split settings from #6885 were not being honored at all.
Also:
* Made sure "pagewidth" is actually the default zoom mode again, "full" had sneaked in as the default state of the zoom type toggle).
* Display human-readable values in the "Make as default" popup, instead of the raw, meaningless numerical setting.
* Disable zoom options when reflow is enabled, and restore 'em properly when it's disabled.
Fix#7461, #7228, #7192